Management of Legionella in Water Systems (2019)Water Science and Technology Board
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Webinar Briefing PowerPoint
Webinar Briefing Recording
Legionnaires' disease, a pneumonia caused by the Legionella bacterium, is the leading cause of reported waterborne disease outbreaks in the United States. Legionella occur naturally in water from many different environmental sources, but grow rapidly in the warm, stagnant conditions that can be found in engineered water systems such as cooling towers, building plumbing, and hot tubs. The report estimates that the incidence of the disease is much higher than the reported incidents, with an estimated 52,000 to 70,000 cases each year. Three to 33 percent of all cases are fatal. Studies also show the incidence of Legionnaires' disease increased five-fold from 2000 to 2017.
The report concludes that stronger U.S. policies and guidance is needed to combat this growing problem. The report recommends that, for all types of buildings, hot-water heater temperatures should be maintained above 60°C (140°F), and the hot-water temperature to distal points should exceed 55°C (131°F). Distal points are connected to fixtures like faucets and thermal mixing valves, upstream of the tap. All public buildings such as hotels, businesses, schools, apartments, and government buildings should be required to have a water management plan that includes regular monitoring for Legionella. Other recommendations include eliminating the use of low-flow fixtures in hospitals and long term care facilities, development of guidance for homeowners, registering and monitoring of cooling towers, and a required minimum level of disinfectants in public water systems.